Piston pump for corrosive liquids



Patented Jan. 1, 1929.

UNITED STATES ATTILIO FERRARIS, OF TURIN, ITALY.

PISTON PUIVIP FOR CORROSIVE LIQUIDS.

Application filed September 29, 1927, Serial No. 222,876, and in Italy April 20, 1927.

My invention relates to pistou pumps for corrosive liquids. of the class described in my prior Patent- No. 1.159.201 and has for its object to provide an .improved pump which will avoid some drawl'iaeks thereof.

In my prior pump, like any pistou pump generally. a liquid loss was Jfound by leakage through the stutling-box packing. having substantially the same diameter as the suction and force cylinder. and thereby the pump was objectionable because of a considerable wear and tear ot the stuiiing-box paekinla's, requiring to be firmly tightened in order to compensate the plays, whereby the friction work was considerably increased.

In order to obviate the said drawliaek and to avoid any liquid loss. while redueing as much as possible the packing wear and the friction work. my present invention provides an air chamber or counter-pressure chamber over the piston body, a relatively small stuiiing box providing for the tightness of said chamber, said stufng box being furnished with a packing which only surrounds the piston rod and is adapted to merely prevent low-pressure air leakages from said chamber, so that any water-tight joint is dispensed with.

In the attached drawing, forming a part of this specification, I have shown an embodiment of my invention, wherein: Fig l is a vertical sectional view of my improved piston pump, and Fig. 2 shows a detail thereoi." at an enlarged scale.

Referring to the drawing, A is a piston body having a piston rod G and working in a cylinder B over a' suitable amount of greasy or lubricating substance, such as petroleum jelly or oil for example, as an intermediate cushion' between the corrosive liquid (denoted by Acid in Fig. l) and the metal piston body A. i

According to my present invention, I provide no packing on the piston body A, so as to dispense with any waterstight joint between the piston periphery and cylinder wall, which shall merely be worked and finished as usual to slidably iit in each other as exactly as possible.

At the upper end position of the suction stroke of the piston, a chamber C of suitable size is provided between the piston and the head or cover of the cylinder. D is an equalizing air valve arranged in the cylinder cover of the pump, and E is a liquid delivery -valve arranged in the piston body and opening downwards, both valves being provided with suitable adjusting means, such as springs and the like.

The chamber C is adapted to enclose an amount of air, sucked in through the air valve D, at a. pressure which shall be suiiicient to force down, through the Valve E, any liquid which might have passed through the clearance between the piston and cylinder walls to the upper face of the piston, in spite of the adjustment thereof being as ae curate as possible.

The pressure referred to, or counter-pressure. in the chamber C at the upper end position of the piston will automatically be defined by the increase in theliquid level over the upper face of the piston, the raising liquid causing the air space to be reduced and the pressure therein to increase up to the adjustment value of the valve Ef Upon reaching such value, the valve opens and allows the liquid to flow downwards, both by normal operation and when-subsequent to any stoppage of the pump-a considerable amount ot liquid should have passed over the piston, due to the return pressure liquid column. Under these conditions the pump is adapted to operate` indefinitely, without requiring any control or adjustment of the packings.

Cn the other hand, the valve D allows the air suction in the chamber C during the suction or lowering 'stroke of the piston, and the supply of such amount of air as might have escaped through any fault of tightness in thev packing of the stuiiing box F, while remaining air-tight under the counter-pressure.

It will be seen that the large stuiiing-box and objectionable packings of my old known construction has been replaced here by the relatively little stuiiing box F, adapted to merely prevent low pressure air leakages from the counter-pressure chamber.

By dispensing with any large stuffing box, and by avoiding thereby the losses due to the piston beingr acted upon by pressure liquid, any liquid leakage is prevented, while avoiding aty the same time both the friction of large packings and repairs thereof, the packing of my present construction being confined to a little one which only surrounds the piston rod. so that considerable working economy and low power consumption is provided.

What I claim is: l A

A pump for corrosive liquids comprising I e cylinder anda piston movable therein in.

i a. one-way valve opening directly from the atmosphere into said air chamber, a piston rod connected to said piston centrally thereof and having a small dlameter- [relative to that of the piston, a one-way valve in said piston 10 rod permitting iluid to passy from said air chamber to said oil chamber, a chamber having its upper part in communication with the lower end of said cylinder land adapted to contain a corrosive liquid in its lower part and oil'in its upper part, and an inlet and an outlet for the corrosive liquid.

In testimony whereof, I have set my hand at Turin, Italy, this 16th day of September,

' y ATTILIO FERRARIS. 

